The present invention relates to a contact lens for use in vitreoretinal surgery, sometimes referred to as vitrectomy lens, and more particularly, to method and structure for maintaining contact lens position on an eye during surgery.
Vitreoretinal surgery is generally performed by a surgeon using an ophthalmic microscope to peer into the eye. Because of the optics of the eye itself, it is difficult to focus the microscope onto parts of the eye that are toward the rear portion. For this reason, surgeons typical employ a separate lens that can be placed directly on the eyeball and allow focusing to be extended to the retina and other areas in the back of the eyeball. However, the lens placed on the eyeball floats on a thin layer of fluid and tends to slide about the surface of the eye. One method that has been used to overcome this sliding displacement and hold the lens in place has been for an assistant to constantly monitor the lens position and using a rod or other extension to push the lens back to a desired location. Such assistant need be experienced in vitreoretinal surgery in order to perform this task.
One method that has been developed for overcoming the problem of lens movement is disclosed in U.S. Pat. No. 5,963,301. in that patent, the lens is constructed with a flange that is shaped to conform to the general curvature of an average eye. Accordingly, the flange generally will not seat in a sealing arrangement on the surface of the eye without being pressed down. The flange is large enough to extend over the sclera of the eye and has a fixed radius of curvature that is substantially flatter than the curvature of contact surface of the lens so that the lens device tends to be stabilized and centered over the cornea of the eye. The flange is formed with a number of peripheral opening or recesses that are sized to accommodate various types of instruments that may need to be inserted into the eye during surgery. The flange may also be formed with fittings to which a vacuum may be applied in order to pull the flange into contact with the eye by creating a vacuum between the flange and eye to better hold the lens device in position.
Another method that has been developed for overcoming the problem of contact lens movement during surgery is disclosed in U.S. Pat. No. 6,120,147. In this patent, the authors recognize that there are issues with the typical glass or inflexible contact lens and therefore propose to replace that lens with a flexible lens having a relatively flexible flange that can that can flex relative to the contact lens without deforming the flexible lens. The flange in this instance is formed with a curvature that is less than the radius of curvature of the average sclera so that it can be secured to a range of different size eyes. In use, this lens device is pressed down into full contact with the eye so that the lens becomes fixed in place by capillary action. In order for this to be successful, it is necessary for the lens and flange to be kept to a very light weight.